feat(#62): ideology / government-type change (v0.39.0)

Add a per-nation free-form ideology (form of government) field and a
TurnResult.ideology lever (coups / revolutions / reforms / constitutional
changes) with a deterministic -5 stability dip and political narration.

- shared/types.ts: Nation.ideology?: string (optional/additive)
- shared/protocol.ts: IdeologyChange / IdeologyOps, IDEOLOGY_STABILITY_EFFECT
  = -5, TurnResult.ideology (required, between leaders and markers),
  nationForPrompt now carries ideology
- server/engine.ts: validateIdeologyOps (exported, never throws),
  applyIdeologyChange (resolve -> set field -> -5 dip mirrored to regions +
  re-derived -> political event), ideology block in applyTurnResult after
  leaders / before markers, isMeaningful + validateTurnResult + system prompt
  + runTurn unclear fallback
- server/stub.ts: StubPayload gains ideology; deterministicTurn returns
  ideology: { changes: [] } (never changes one, e2e unaffected)
- Tests: engine.test.ts (validate / isMeaningful / applyTurnResult /
  buildUserPrompt), protocol.test.ts (constant + nationForPrompt),
  db.test.ts (legacy load + round-trip); every TurnResult fixture updated
- package.json -> 0.39.0; CHANGELOG v0.39.0 entry

shared/types.ts

@@ -88,6 +88,18 @@ export interface Nation {
    * each change carries a deterministic stability effect + a narration event.
    */
   leader?: { name: string };
+  /**
+   * The nation's current form of government (v0.39, #62) — a free-form label
+   * such as `"democracy"`, `"fascism"` or `"military junta"`. Optional — a
+   * legacy game (or a nation the LLM has never given an ideology to) has none,
+   * which is the "no recorded government" baseline. The LLM changes it via
+   * `TurnResult.ideology` (coups / revolutions / reforms / constitutional
+   * changes, see `IdeologyChange` in `protocol.ts`); each change carries a
+   * deterministic stability dip + a political narration event. Distinct from
+   * the v0.32.0 takeover (which renames the nation) and from `leader` (who is
+   * in charge): only the form of government and stability move.
+   */
+  ideology?: string;
 }
 
 /** Categories a narrative event can take. */